1. Field of the Invention
The invention relates to a control device and control method for a cooling system and, more particularly, to a control device and control method for a cooling system that cools a heat generating source.
2. Description of Related Art
In recent years, hybrid vehicles, fuel cell vehicles, electric vehicles, and the like, that travel with the use of driving force of a motor become a focus of attention as one of measures against environmental issues. In such vehicles, electrical devices, such as a motor, a generator, an inverter, a converter and a battery, exchange electric power to generate heat. Therefore, these electrical devices need to be cooled. Then, there has been suggested a technique that utilizes a vapor compression refrigeration cycle, which is used as a vehicle air conditioner, to cool a heat generating element.
For example, Japanese Patent Application Publication No. 2007-69733 (JP 2007-69733 A) describes a system in which a heat exchanger that exchanges heat with air-conditioning air and a heat exchanger that exchanges heat with a heat generating element are arranged in parallel with each other in a refrigerant line routed from an expansion valve to a compressor and refrigerant for an air conditioner is utilized to cool the heat generating element. Japanese Patent Application Publication No. 2005-90862 (JP 2005-90862 A) describes a cooling system in which a heat generating element cooling unit for cooling a heat generating element is provided in a bypass line that bypasses the decompressor, evaporator and compressor of an air-conditioning refrigeration cycle.
Japanese Patent Application Publication No. 2006-179190 (JP 2006-179190 A) describes an in-vehicle battery pack. The in-vehicle battery pack includes a case body and an evaporator of an air-conditioning refrigeration cycle. The case body includes a layer cell assembly and an air duct inside. The evaporator is installed inside the case body in order to cool cooling air flowing through the air duct. Japanese Patent Application Publication No. 2002-313441 (JP 2002-313441 A) describes a battery cooling system. In the battery cooling system, an evaporator that is cooled by refrigerant supplied from a refrigeration cycle of an air-conditioning system via a cooling bypass line is arranged in a cooling line to which part or whole of a battery is exposed, and air in the cooling line is circulated by an air blower.
On the other hand, as for a control device for a hybrid vehicle, Japanese Patent Application Publication No. 2008-239079 (JP 2008-239079 A) describes a technique as follows. An abnormality of a driving battery is monitored. When an abnormality other than a temperature-related abnormality has been detected, the vehicle is shifted into a batteryless drive mode. Then, when a temperature abnormality of the driving battery has been detected in the batteryless drive mode, the vehicle is stopped.
JP 2007-69733 A, JP 2005-90862 A, JP 2006-179190 A and JP 2002-313441 A do not describe that the heat generating element is continuously cooled when an abnormality has occurred in the refrigeration cycle, such as an abnormality of a compressor and a shortage of refrigerant circulating through the refrigeration cycle. Therefore, when an abnormality occurs in the refrigeration cycle, cooling performance for cooling the heat generating element decreases, and the temperature of the heat generating element problematically increases.